There are also specific forms of depression which include: dysthymia-a mild form of depression, lasting at least 2 years, bipolar affective disorder- also known as manic depression or just bipolar disorder. This is a condition that causes mood swings. Your mood varies from excitement to depression and despair. You may also have hallucinations. Seasonal affective disorder (SAD) is another type of depression with a seasonal pattern, occurring most commonly in the winter months. Postnatal depression develops 2-3 weeks after childbirth and lasts for months or even years.
Attribution: BUPA